Optoelectronic devices with intelligent transmitter modules

ABSTRACT

An optoelectronic device can implement an intelligent transmitter module (“ITM”), rather than a conventional TOSA, for the transmission of optical data signals. The ITM can include an optical transmitter, a CDR and driver IC, and a microcontroller and/or linear amplifier. Space available in the optoelectronic device due to using an ITM rather than a TOSA and PCB-bound CDR, driver, microcontroller, and/or linear amplifier can be used for the inclusion of one or more electronic and/or optical components. Electronic components that can be included in a device with an ITM include: an FPGA, a DSP, a memory chip, a digital diagnostic IC, a video IC, a wireless interface, and an RF interface. Optical components that can be included in a device with an ITM include: a VOA, an SOA, a MUX, a DEMUX, a polarization controller, and an optical power monitoring device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/968,581, entitled INTELLIGENT TRANSMITTER MODULE, filed onJan. 2, 2008, which in turn claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/940,043, entitled INTEGRATED TRANSMITTEROPTICAL SUBASSEMBLY, filed on May 24, 2007. The foregoing applicationsare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates generally to devices for high speed datatransmission. More particularly, embodiments of the invention concernoptoelectronic devices having one or more intelligent transmittermodules and specialized functionality.

2. The Relevant Technology

Computing, telecom and networking technology have transformed our world.As the amount of information communicated over networks has increased,high speed transmission has become ever more critical. Many high speeddata transmission networks rely on optical transceivers and similardevices for facilitating transmission and reception of digital dataembodied in the form of optical signals over optical fibers. Opticalnetworks are thus found in a wide variety of high speed applicationsranging from modest Local Area Networks (“LANs”) to backbones thatdefine a large portion of the infrastructure of the Internet.

Typically, data transmission in such networks is implemented by way ofan optical transmitter, such as a laser or Light Emitting Diode (“LED”).The optical transmitter emits light when current is passed through it,the intensity of the emitted light being a function of the magnitude ofthe current. Data reception is generally implemented by way of anoptical receiver, an example of which is a photodiode. The opticalreceiver receives light and generates a current, the magnitude of thegenerated current being a function of the intensity of the receivedlight.

Various other components are also employed by the optical transceiver toaid in the control of the optical transmit and receive components, aswell as the processing of various data and other signals. For example,such optical transceivers typically include a driver (e.g. referred toas a “laser driver” when used to drive a laser signal) configured tocontrol the operation of the optical transmitter in response to variouscontrol inputs. The optical transceiver also generally includes anamplifier (e.g. often referred to as a “post-amplifier”) configured toamplify the channel-attenuated received signal prior to furtherprocessing. A controller circuit (hereinafter referred to as the“microcontroller”) controls the operation of the laser driver andpost-amplifier. A clock and data recovery circuit (hereinafter referredto as the “CDR”) may also be used in telecommunication applications(e.g., SONET networks) to equalize and retime electrical data signalsprior to transmission as optical signals.

Two often conflicting demands in the market for components used inoptical networks are the demands for higher transmission speeds andminiaturization. The conflict is evident, for example, in trying todesign modules suitable for use in SONET applications that can alsoachieve 10G and above telecommunication data transmission speeds. Thehigh-speed nature of signal transmission demands a minimum number ofelectronic interconnects with a short path for electrical transmissionbetween the components of the module. Electronic interconnects in theform of leads, flex circuits, and piece-wise continuous groundconnections pose a major challenge in meeting SONET jitter performancedue to reflections and bandwidth limitations. Electromagnetic complianceon the transmit side (e.g., CDR, laser driver, transmitter) is also amajor challenge due to high frequency signal generation and reflectionsat each interface, which can be major sources of EMI emissions at 10 Gdata rates.

The current dominant technology for achieving long haul (>80 km) opticaltransmission at and above 10 G data rates implements Lithium NiobateMach-Zehnder and InP Mach Zehnder modulators. Typically, however,modules implementing this technology are relatively expensive, large,and power hungry. One alternative solution for achieving 10 G data ratesin applications less than 100 km involves the use of directly modulatedlasers (“DMLs”) or externally modulated lasers (“EMLs”), which are oftenless expensive, smaller and less power hungry than Lithium NiobateMach-Zehnder and InP Mach Zehnder modulators. However, adiabatic chirpgenerated in distributed feedback lasers due to RF pickup and backreflection and transient chirp in the modulator section cause rapiddistortion of the eye after fiber propagation. As a result, conventionalDMLs and EMLs remain limited to applications less than 100 km.

The subject matter claimed herein is not limited to embodiments thatsolve any disadvantages or that operate only in environments such asthose described above. Rather, this background is only provided toillustrate one exemplary technology area where some embodimentsdescribed herein may be practiced.

BRIEF SUMMARY OF THE INVENTION

These and other limitations are overcome by embodiments of the inventionwhich relate to systems and methods for high speed data transmission.More particularly, embodiments of the invention are directed tooptoelectronic devices having an intelligent transmitter module (“ITM”)rather than a conventional TOSA, CDR, driver, and microcontroller and/orlinear amplifier. Briefly, an ITM is a TOSA-like device that can includean optical transmitter, a CDR and driver IC, and a microcontrollerand/or linear amplifier. Similar to a conventional TOSA, an ITM receivesan electrical data signal and emits an optical data signal. In contrastto a conventional TOSA, however, an ITM additionally includes electroniccomponents for equalizing and retiming the electrical data signal andperforming waveform shaping of the electrical data signal. Embodimentsof an ITM can also include electronic components for at least one of:monitoring and controlling the ITM (e.g., using a microcontroller), andamplifying the electrical data signal (e.g., using a linear amplifier)prior to being received by the optical transmitter.

Some or all of the above-described electronic components can beintegrated within the ITM and configured in a manner that reduces theamount of space they occupy and the amount of power they consumecompared to their conventional counterparts. Consequently, as comparedto an optoelectronic device with a conventional TOSA, an optoelectronicdevice with an ITM can include one or more additional electronic and/oroptical components without requiring additional space and/or powerbudget. Electronic components that can be included within anoptoelectronic device having an ITM include: an FPGA, a DSP, a memorychip, a digital diagnostic IC, a video IC, a wireless interface, and anRF interface. Optical components that can be included within anoptoelectronic device with an ITM include: a VOA, a booster orpre-amplifier (e.g., an SOA), an optical multiplexer, an opticaldemultiplexer, a polarization controller, and an optical powermonitoring device (e.g., a photodetector).

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by the practice of the invention. Thefeatures and advantages of the invention may be realized and obtained bymeans of the instruments and combinations particularly pointed out inthe appended claims. These and other features of the present inventionwill become more fully apparent from the following description andappended claims, or may be learned by the practice of the invention asset forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 illustrates a conventional optoelectronic device;

FIG. 2 illustrates an optoelectronic device with an ITM and an on-boardFPGA;

FIG. 3 illustrates an optoelectronic device with an ITM and an on-boardmemory chip;

FIG. 4 illustrates an optoelectronic device with an ITM and an on-boarddiagnostic IC;

FIG. 5 illustrates an optoelectronic device with an ITM and an on-boardvideo IC;

FIG. 6 illustrates an optoelectronic device with an ITM and an on-boardwireless interface;

FIG. 7 illustrates an optoelectronic device with an ITM and an on-boardRF interface;

FIG. 8 illustrates an optoelectronic device with an ITM and a variableoptical attenuator;

FIG. 9 illustrates an optoelectronic device with an ITM, an opticalbooster, and an optical pre-amplifier;

FIG. 10 illustrates a multi-channel optoelectronic device with multipleITMs, an optical multiplexer and an optical demultiplexer;

FIG. 11 illustrates an optoelectronic device with an ITM and apolarization controller;

FIG. 12 illustrates an optoelectronic device with an ITM and an opticalpower monitor;

FIGS. 13A and 13B illustrate the effects on channel power ofwavelength-dependent amplification/attenuation and awavelength-dependent variable optical attenuator;

FIGS. 14A and 14B illustrate embodiments of an intelligent transmittermodule;

FIG. 15A illustrates an example CDR and driver IC according to oneembodiment of the invention;

FIG. 15B illustrates one embodiment of a CDR that can be implemented inthe CDR and driver IC of FIG. 15A;

FIG. 16 is a diagram of a linear amplifier that can be implemented in anintelligent transmitter module, according to one embodiment;

FIG. 17 illustrates one embodiment of a laser with managed chirpaccording to the invention; and

FIG. 18 is a diagram of a microcontroller that can be implemented inembodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe various aspectsof exemplary embodiments of the invention. It should be understood thatthe drawings are diagrammatic and schematic representations of suchexemplary embodiments and, accordingly, are not limiting of the scope ofthe present invention, nor are the drawings necessarily drawn to scale.

Embodiments of the invention relate to optoelectronic devices such astransceivers and transponders that implement an intelligent transmittermodule (“ITM”) rather than a conventional transmitter opticalsubassembly (“TOSA”) for the transmission of optical signals. Briefly,an ITM according to one embodiment of the invention includes an opticaltransmitter and one or more electronic components typically found on theprinted circuit board (“PCB”) of a conventional optoelectronic device,such as a CDR and laser driver. The ITM may also include a linearamplifier and/or a microcontroller. By removing the one or moreelectronic components from the PCB, real estate is made available on thePCB for the addition of one or more electronic components, such as afield programmable gate array (“FPGA”), a digital signal processor(“DSP”), a memory chip, a diagnostic integrated circuit (“IC”), a videoIC, a wireless network interface and an RF on fiber interface.Alternately or additionally, the size of the PCB can be reduced to makeroom within an optoelectronic device for one or more optical components,such as: a variable optical attenuator (“VOA”), a semiconductor opticalamplifier (“SOA”), an optical multiplexer (“MUX”) and/or demultiplexer(“DEMUX”), and a polarization controller.

Embodiments of the invention can be implemented in variousoptoelectronic devices. As used herein, the term “optoelectronic device”includes devices having both optical and electrical components. Examplesof optoelectronic devices include, but are not limited to transponders,transceivers, transmitters, and/or receivers. Optoelectronic devices canbe used, for example, in telecommunications networks, local areanetworks, metro area networks, storage area networks, wide areanetworks, and the like. The principles of the present invention may beimplemented in optoelectronic devices of any form factor currentlyavailable or that may be developed in the future for 10 G, 40 G, and 100G signaling, without restriction. It will be appreciated, however, thatthe optoelectronic devices need not comply with standardized form factorrequirements and may have any size or configuration necessary accordingto a particular design. The principles of the present invention aresuitable for use with, for example, 10 G, 40 G and other transmissionspeeds.

I. Conventional Optoelectronic Devices

FIG. 1 illustrates some of the shortcomings of an optoelectronic device100 commonly used in the prior art for optical communication. The device100 of FIG. 1 is shown in simplified block diagram form and maycorrespond to a transceiver or transponder. As used herein, a“transceiver” is an optoelectronic device that converts one or morereceived serial electrical signals to a corresponding number of serialoptical signals and/or that converts one or more received serial opticalsignals to a corresponding number of serial electrical signals. Incontrast, a “transponder” converts two or more received parallelelectrical signals to a fewer number of serial optical signals and/orconverts one or more received serial optical signals to a greater numberof parallel electrical signals.

Whether implemented as a transceiver, transponder, or other device, theoptoelectronic device 100 includes a substrate or PCB 110 upon which aplurality of active and/or passive circuitry components, such as a laserdriver 112 and post amplifier 114, are connected or mounted forprocessing electrical data signals. The device 100 additionally includesa TOSA 120 for emitting optical signals onto a fiber optic (or otheroptical) network and a ROSA 130 for receiving optical signals from thefiber optic network. Although not illustrated, the TOSA 120 includes anoptical transmitter such as a laser and the ROSA 130 includes an opticalreceiver such as a photodiode. The TOSA 120 and/or ROSA 130 can bemounted on the PCB 110 or connected to the PCB 110 through flexcircuits, leads, and the like.

If the device 100 is implemented as a transceiver, it may include atransmit clock and data recovery circuit (“CDR”) 116 for equalizing andretiming an outbound electrical data signal 102 and/or a receive CDR forequalizing and retiming an inbound electrical data signal 106. In thisembodiment, the transceiver 100 can receive a serial data-carryingelectrical signal 102 from a host (not illustrated), which can be anycomputing system capable of communication with the device 100, fortransmission as a serial data-carrying optical signal. The electricalsignal is first provided to the transmit CDR 116 where the CDR 116equalizes and retimes the electrical data signal using a reference clockfrom the host or using the electrical data signal itself. The equalizedand retimed electrical data signal 104 is provided to the driver 112which drives the TOSA 120 to emit an optical signal representative ofthe electrical data signal 102. In addition, the transceiver 100 canreceive a serial data-carrying optical signal using the ROSA 130. TheROSA 130 transforms a received optical signal into a serial electricalsignal 106 which can be amplified by the post-amplifier 114 prior tobeing provided to the host.

If the device 100 is implemented as a transponder, it may alternately oradditionally include a transmit serializer/deserializer (“SERDES”) 116for serializing two or more parallel data signals and/or a receiveSERDES 118 for deserializing one or more serial data signals. In thisembodiment, the transmit SERDES 116 receives two or more parallel datasignals 102 from the host at a first (slow) signal rate and provides asoutput one or more serial data signals 104 at a second (fast) signalrate. The serial data signal 104 is provided to the laser driver 112which drives the TOSA 120 to emit an optical signal representative ofthe serial data signal 104. Additionally, the transponder 100 canreceive an optical signal using the ROSA 130, which transforms thereceived optical signal into a serial electrical signal 106. The receiveSERDES 118 deserializes the serial electrical signal 106 into two ormore parallel data signals 108 which are provided to the host.

One skilled in the art will appreciate that the transmit and receiveSERDES 116, 118 can be single channel (e.g., for serializing a pluralityof parallel signals into a single serial signal or for deserializing asingle serial signal into a plurality of parallel signals) ormulti-channel (e.g., for serializing a plurality of parallel signalsinto two or more serial signals or for deserializing two or more serialsignals into a greater number of parallel signals) SERDES and that acorresponding number of components can be included in the transponder100 when the SERDES 116, 118 are multi-channel SERDES. For instance, ifthe SERDES 116 serializes M parallel data signals into N serial datasignals (where M is greater than N), N laser drivers and N TOSAs can beprovided for handling the N serial signals.

Further, the SERDES 116, 118 may comply with certain interfacestandards. For instance, the SERDES 116, 118 may be compliant with theSFI-4.1 or SFI-5.1 interface standards, which specify conversion of 16parallel electrical data lanes and a 17^(th) deskew lane (each at ˜622MHz or ˜2.5 GHz, respectively) to a single serial data lane (at ˜10 GHzor ˜40 GHz, respectively) and vice versa. Alternately, the SERDES 116,118 may comply with the SFI-5.2 interface standard, which specifiesconversion of 4 electrical data lanes and a 5^(th) deskew lane (each atabout 10 GHz) to a single serial data lane (at ˜40 GHz), and vice versa.Other suitable interface standards may exist according to a particularembodiment and the invention should not be limited to the interfacestandards explicitly stated.

Returning to FIG. 1 and referring to optoelectronic devices generally,whether implemented as transceivers or transponders, some conventionaloptoelectronic devices 100 additionally include a microcontroller 119which can be used for, among other things, optimizing the performance ofthe device 100. For example, the microcontroller 119 controls one ormore of: the temperature of the optical transmitter within the TOSA 120,the optical transmitter bias current, the optical transmitter modulationamplitude, and settings on the transmit CDR/SERDES 116, receiveCDR/SERDES 118, driver 112, post-amplifier 114, and the like.Additionally, the microcontroller 119 can communicate with the host overan interface 109, such as I²C, SPI, MDIO, 1-wire, and the like, in orderto receive control signals and/or to transmit data/alarms.

The optoelectronic device 100 may include additional components, such asan optical fiber receptacle, latching mechanisms, laser bias circuitry,TEC control circuitry, and the like or any combination thereof. Thesecomponents and their disposition and function within a conventionaldevice 100 are well known in the art and will not be described infurther detail to avoid unnecessarily obscuring the invention.

The components of the device 100 can be protected by a covering orenclosure 140 such as a shell or housing configured to comply with astandardized form factor such as XENPAK, SFP, XFP, MSA300, MSA200, andthe like. Alternately or additionally, the device 100 may comply withcertain telecommunications standards, such as SONET/SDH, and the like.It is understood that compliance with standardized form factors and/ortelecommunication standards may limit the size, and/or the power budget,for the device 100. Consequently, a conventional device 100 typicallylacks the real estate and/or power budget to include components inaddition to those already mentioned.

II. Optoelectronic Devices Having An Intelligent Transmitter Module

Turning to FIGS. 2-12, various optoelectronic devices are illustratedthat overcome these and other limitations of the prior art by using anintelligent transmitter module, rather than a conventional TOSA, for thetransmission of optical signals. As previously mentioned and asdescribed in greater detail below, embodiments of an ITM can include anoptical transmitter, a CDR and driver, and a microcontroller and/orlinear amplifier. By integrating the electronic components (e.g., CDR,driver, microcontroller, linear amplifier) into the same package as theoptical transmitter, numerous advantages are obtained. For purposes ofthe present discussion, a primary advantage is a net reduction inrequired PCB real estate and power dissipation relative to aconventional optoelectronic device. This advantage is obtained because(1) the CDR, driver, and microcontroller and/or linear amplifier are noton the PCB, rather they are integrated with the optical transmitter, and(2) the ITM uses less net power than the CDR, driver, microcontroller,linear amplifier and TOSA of a conventional device. Note that althoughan ITM may be larger than a conventional TOSA, requiring reduction inthe size of a PCB or other components to accommodate the ITM, the amountof real estate made available on the PCB exceeds the amount of realestate eliminated from the PCB.

Each of the optoelectronic devices illustrated in FIGS. 2-12 includes aPCB, an ITM, and a ROSA. Each of the optoelectronic devices mayadditionally include one or more SERDES (transmit and/or receive) and/ora receive CDR, depending on the particular implementation of theoptoelectronic device. Further, the optoelectronic devices illustratedin FIGS. 2-12 can be bidirectional optoelectronic devices capable oftransmitting and receiving optical signals. Note, however, that theprinciples of the invention can also be implemented in unidirectionaloptoelectronic devices capable of transmitting optical signals but notreceiving optical signals, or vice versa.

With particular attention to FIG. 2, one embodiment of an optoelectronicdevice 200 is illustrated having available space for an electroniccomponent not provided in conventional optoelectronic devices. Thedevice 200 includes a PCB 210, ITM 220 and ROSA 230. A post amplifier214 can be provided on the PCB 210 to amplify an inbound electricalsignal and a receive CDR (and/or SERDES) 218 can be provided to retime(and/or deserialize) the inbound electrical signal prior to providing itto a host. The optoelectronic device 200 may additionally include afield programmable gate array (“FPGA”) 216 coupled to the PCB 210.

Many times, users of optoelectronic devices desire particularfunctionality from devices that is not provided by device manufacturers.Consequently, device users have to be satisfied with what is availableon the market. Alternately, device users can request the inclusion of anapplication specific integrated circuit (“ASIC”) and/or firmware to beused by a microcontroller in order to obtain the desired functionality.However, this alternative is usually costly and not realistic for manydevice users. Further, inclusion of an ASIC may not be possible due tothe lack of available real estate and/or power budget in a conventionaloptoelectronic device.

According to the present example, however, an FPGA 216 can be providedto permit programming of the desired functionality after manufacture.The programming of the FPGA can be performed by the manufacturer and/orby the device user. The FPGA can include a central processing unit.Since the CDR, driver, and other components can be included in the ITMrather than on the PCB 210, real estate may be available on the PCB 210for the FPGA 216. Accordingly, the device 200 can be configured tocomply with, e.g., the XFP MSA, the 300 pin MSA, and the like, whileadditionally including an FPGA.

In one example embodiment, the FPGA 216 can be programmed to function asa digital signal processor (“DSP”). In other words, the FPGA 216 can beprogrammed to implement digital signal processing algorithms. In thisembodiment, the FPGA can function to improve the quality of electricaldata signals received from, and/or sent to, the host. One skilled in theart will appreciate that electrical data signals received from the host,and/or from the ROSA 230, will include noise resulting from transmissionthrough electrical circuits/traces between the host, and/or the ROSA230, and the PCB. The FPGA 216 can eliminate irregularities in theelectrical data signals caused by noise, which minimizes the number ofbit errors per unit time. For instance, the FPGA can sample and quantizean outbound electrical data signal (e.g., using an A2D). Quantization ofthe signal includes rounding the sampled values to expected or predictedvalues, which tends to eliminate noise. The quantized signal can then beconverted back to an analog signal (e.g., using a DAC) and provided tothe ITM 220.

Turning now to FIG. 3, another embodiment of an optoelectronic device300 is illustrated having available space for an electronic componentnot provided in a conventional optoelectronic device. The device 300 caninclude a PCB 310, ITM 320, ROSA 330, post amplifier 314, and receiveCDR (and/or SERDES) 318. The optoelectronic device 300 additionallyincludes a memory chip 316 coupled to the PCB 310. The memory chip 316may be volatile and/or non volatile memory, and may comprise RAM, ROM,PROM, EPROM, EEPROM, flash memory, and the like or any combinationthereof. In one embodiment, the memory 316 is used to store microcodethat can be executed by a microcontroller implemented on the PCB 310and/or inside the ITM 320. Alternately or additionally, the memory 316can be used to store information identifying the device 300 (such asdevice type, capability, serial number, and the like), operationalparameters/settings, and the like or any combination thereof.

Turning now to FIG. 4, another embodiment of an optoelectronic device400 is illustrated which can have an electronic component not availablein conventional optoelectronic devices. The optoelectronic device 400can include a PCB 410, ITM 420, ROSA 430, post amplifier 414, andreceive CDR (and/or SERDES) 418. The device 400 can additionally includea digital diagnostic IC 416 coupled to the PCB 410. The digitaldiagnostic IC 416 can allow for better fault isolation and/or errordetection.

The digital diagnostic IC 416 may be used to perform various tasks andto generate monitoring and operating data. In some embodiments, adigital diagnostic IC or other means for generating monitor andoperating data and performing other tasks may be required for compliancewith certain MSA standards. These tasks and data may include one or moreof the following:

-   -   Setup functions. These generally relate to the required        adjustments made on a part-to-part basis in the factory to allow        for variations in component characteristics such as transmitter        threshold current.    -   Identification. This refers to information identifying the        optoelectronic device type, capability, serial number, and        compatibility with various standards. This information may        additionally include sub-component revisions and factory test        data. The information may be accessed using, e.g., a serial        communication standard.    -   Eye safety and general fault detection. These functions are used        to identify abnormal and potentially unsafe operating parameters        and to report these to the host and/or perform transmitter        shutdown, as appropriate.    -   Temperature compensation functions. For example, compensating        for known temperature variations in key transmitter        characteristics such as slope efficiency.    -   Monitoring functions. Monitoring various parameters related to        the optoelectronic device operating characteristics and        environment. Examples of parameters that may be monitored        include DC supply voltage, transmitter bias current, transmitter        output power, receiver power levels, supply voltage and        temperature. Ideally, these parameters are monitored and        reported to, or made available to, a host and thus to the user        of the optoelectronic device.    -   Power on time. The optoelectronic device's control circuitry may        keep track of the total number of hours the optoelectronic        device has been in the power on state, and report or make this        time value available to a host.    -   Margining. “Margining” is a mechanism that allows the end user        to test the optoelectronic device's performance at a known        deviation from ideal operating conditions, generally by scaling        the control signals used to drive the optoelectronic device's        active components.    -   Other digital signals. A host may configure the optoelectronic        device so as to make it compatible with various requirements for        the polarity and output types of digital inputs and outputs. For        instance, digital inputs are used for transmitter disable and        rate selection functions while outputs are used to indicate        transmitter fault and loss of signal conditions. The        configuration values determine the polarity of one or more of        the binary input and output signals. In some transceivers, these        configuration values can be used to specify the scale of one or        more of the digital input or output values, for instance by        specifying a scaling factor to be used in conjunction with the        digital input or output value.

Methods and systems for performing digital diagnostic functions areknown in the art and need not be described in detail here. While digitaldiagnostic ICs have been provided in conventional optoelectronic devicesin the past, they have not been provided in conjunction with anintelligent transmitter module 420. Due to the extra real estate on thePCB 410 and/or power budget which may result from implementing an ITM420, the digital diagnostic IC 416 can be larger and include morefunctionality than a conventional digital diagnostic IC. Furthermore, insome embodiments at least some of the digital diagnostic functions canbe performed by a microcontroller included within the ITM 420, as willbe described in greater detail below, thereby permitting the diagnosticIC 416 to perform more diagnostic functions than a conventionaldiagnostic IC.

Turning now to FIG. 5, another embodiment of an optoelectronic device500 is illustrated which can have an electronic component not availablein conventional optoelectronic devices. The optoelectronic device 500can include a PCB 510, ITM 520, ROSA 530, post amplifier 514, andreceive CDR (and/or SERDES) 518. The device 500 can additionally includea video IC 516 coupled to the PCB 510. Inclusion of the video IC 516 mayenable use of the optoelectronic device 500 to transmit and (optionallyreceive) video signals such as cable and satellite television signals,and the like, over optical fiber. The video IC 516 may comprise, e.g., avideo decoder, a video encoder, video noise-reduction FIFOs, an LCDgraphic display controller, video FIFOs, a video amplifier, a videofilter, and the like or any combination thereof.

The optoelectronic device 500 may enable the transmission of videosignals using optical fiber. It is appreciated that optical fiber hasmuch lower signal loss, is much lighter and is much less expensive thanmaterials (e.g., coaxial cable) conventionally used for video signaldelivery.

With attention now to FIG. 6, an example optoelectronic device 600 isillustrated which can have a wireless interface 616 coupled to the PCB610 for transmitting and/or receiving wireless signals. The wirelessinterface 616 may include an antenna and may be configured to transmitand/or receive wireless signals to and/or from a wireless network, suchas IEEE 802 related networks (e.g., WiFi, LMDS, WiMAX), cellularnetworks, satellite networks, terrestrial RF networks (e.g., AM, FM) andthe like or any combination thereof. In one embodiment, the wirelessinterface 616 can comprise a wireless transceiver.

The device 600, for example, may receive wireless data signals foroptical transmission over an optical fiber using the ITM 620. Or, thedevice 600 can additionally or alternatively receive optical datasignals for transmission as wireless signals using the wirelessinterface 616. The device configuration 600 may enable manyapplications. For example, multiple devices 600 can be connected viafiber optic cables to a head end unit and distributed throughout abuilding or other location to provide a distributed antenna systemthroughout the building. Alternately or additionally, the device 600 canbe implemented as a cellular or PCS transceiver to receive cellular orPCS wireless signals and transmit the wireless signals as opticalsignals over fiber and/or to receive optical signals and transmit themas cellular or PCS wireless signals. Alternately or additionally, thedevice 600 may have a hardwired connection to a host for receivingoutbound electrical data signals (as in a conventional device) and thewireless transceiver 616 can be used to receive and/or transmit controlsignals, and the like, from and/or to the host.

Turning now to FIG. 7, an example optoelectronic device 700 isillustrated for RF on fiber applications. The optoelectronic device 700can include an RF interface 716 coupled to the PCB 710 for receivingand/or transmitting RF signals over hardwired connections. Received RFsignals can be transmitted over optical fiber as optical signals whilereceived optical signals can be transmitted over hardwired connectionsas RF signals.

In the examples disclosed with respect to FIGS. 5-7, a video, wireless,or RF signal can be transmitted/received as an optical signal over anoptical network. One skilled in the art will appreciate that the range,bandwidth, and performance of an optical network may be much better thanin a hardwired or wireless network. Alternately or additionally, ascompared to a cable/satellite TV, wireless, or hardwired RF network,there is no signal egress which ensures data security. Further, opticalnetworks are immune to EMI and RFI interference, in contrast to acable/satellite TV and/or hardwired RF network.

With reference now to FIGS. 8-12, various example optoelectronic devicesare illustrated in which some or all of the real estate made availableon a PCB by removing electronic components conventionally placed on thePCB to an ITM has been eliminated to make room in the optoelectronicdevice for various optical components. For instance, in FIG. 8, theextra real estate on PCB 810 has been eliminated to make room in thedevice 800 for a variable optical attenuator (“VOA”) 840, which can beoperably connected to the optical output of ITM 820. VOAs can be used toadjustably reduce the power level of an optical signal (or signals).Further, the amount of power reduction provided by a VOA may bewavelength dependent.

According to embodiments of the invention, VOA 840 can be used toprovide, e.g., optical pre-emphasis. In many optical networks,Erbium-doped fiber amplifiers (“EDFAs”) can be used as boosters,pre-amplifiers, and/or in-line amplifiers to amplify optical signals.However, EDFAs may display unequal amplification behavior dependent onwavelength. Similarly, attenuation in an optical fiber can be wavelengthdependent. Consequently, different wavelength channels can show adifferent gain over an optical link such that at the end of the opticallink, each wavelength may have a different power and OSNR value. Thiscan be problematic in, e.g., wavelength division multiplexing (“WDM”)systems where multiple signals, each using a different wavelengthchannel, share a single optical fiber.

FIG. 13A illustrates an example of how the power values of differentwavelength channels can vary over an optical link due to unequalamplification and/or attenuation. In this example, while the power ofeach wavelength channel begins at approximately the same value at thebeginning of the optical link (e.g., at the output of the device 800),at the end of the optical link the powers of the wavelength channelshave diverged due to the unequal amplification and/or attenuationexperienced over the optical link. In particular, a first channel 1302Aexperiences less amplification and/or greater attenuation than a fourthchannel 1308A.

In the example of FIG. 8, however, the optical device 800 can includeVOA 840 to provide optical pre-attenuation/pre-emphasis in order toadjust the output power for all wavelengths at the end of the opticallink. In this case, the VOA 840 can attenuate a channel that istransmitted poorly (e.g., channel 1302A of FIG. 13A) less than a channelthat is transmitted well (e.g., channel 1308A). The result is shown inFIG. 13B. As can be seen, at the beginning of the optical link (e.g., atthe output of the VOA) the first channel 1302B is attenuated the leastwhile the second, third and fourth channels 1304B, 1306B and 1308B areincreasingly attenuated. After traveling the length of the optical linkand experiencing unequal amplification and/or attenuation dependent onwavelength, the power of each of the wavelength channels 1302B-1308B isapproximately equal.

The VOA 840 may comprise, for instance, a mechanical VOA having movingparts or a non-mechanical VOA making use of the magneto-optic effect orthe thermo-optic effect of a waveguide, or some other suitableconfiguration. In the embodiment described above (e.g., unequalamplification and/or attenuation dependent on wavelength), anon-mechanical VOA may be preferred as the attenuation of non-mechanicalVOAs can be wavelength dependent. In other embodiments where wavelengthindependence (e.g., wavelength flatness) is desired, however, amechanical VOA may be preferred as an optical filter with low wavelengthdependence can be selected for use in the mechanical VOA.

In FIG. 9, some or all of the extra real estate made available on a PCB910 by removing electronic components from the PCB 910 to an ITM 920 iseliminated to make room for one or more optical boosters and/orpreamplifiers, such as semiconductor optical amplifiers (“SOAs”), whichcan be operably coupled to the optical output and input of the ITM 920and ROSA 930, respectively. In the embodiment 900 of FIG. 9, forinstance, a transmit SOA 940 can be provided as a booster to increasethe output power of the optical signal emitted by the ITM 920, while areceive SOA 950 can be provided as a preamplifier to increase thereceived power of the optical signal received by the ROSA 930. Whileboth a transmit SOA 940 and receive SOA 950 are illustrated in FIG. 9,embodiments of the invention additionally contemplate a single SOAimplemented in either the transmit or receive directions.

SOAs can use a semiconductor to provide the gain medium and can have asimilar structure to Fabry-Perot laser diodes. In contrast to a laserdiode, however, an antireflection coating can be used to reduce endfacereflection and prevent the SOA from lasing. SOAs are electrically pumpedand when an optical signal passes through an SOA, stimulated emissioncan cause an increase in signal photons, thereby amplifying the opticalsignal. SOAs can be much smaller than EDFAs (which are also used toprovide optical amplification) and can be integrated with othersemiconductor devices. Accordingly, while the SOA 940 is shown as adistinct component from the ITM 920, in another embodiment the SOA 940can be integrated with semiconductor devices within the ITM 920, such asthe optical transmitter. The amplification provided by the one or moreSOAs in the embodiment of FIG. 9 can extend the optical reach of thedevice 900. Further, the use of optoelectronic devices 900 having one ormore SOAs 940, 950 can reduce the potential cost and/or complexity of anoptical network by eliminating and/or reducing the need for EDFAs.

FIG. 10 illustrates a multi-channel optoelectronic device 1000 in whichthe real estate savings achieved by implementing a plurality of ITMs canbe used for the inclusion of an optical multiplexer (“MUX”) 1040 and/oran optical demultiplexer (“DEMUX”) 1050 operably coupled to the opticaloutput and input of the ITMs 1020 and ROSAs 1030, respectively. Thedevice 1000 can include a plurality of ITMs 1020A up to 1020N (e.g.,“ITMs 1020”) for emitting a plurality of optical signals, and aplurality of ROSAs 1030A up to 1030N (e.g., “ROSAs 1030”) for receivinga plurality of optical signals. While illustrated with an equal numberof ITMs and ROSAs, the bidirectional optoelectronic device 1000 mayinclude an unequal number of ITMs and ROSAs for use in, e.g., systemswhere transmit and receive traffic is unbalanced.

As shown, the device 1000 is configured to receive up to N data carryingelectrical signals 1002A up to 1002N. After being emitted as N transmitoptical signals by the ITMs 1020A through 1020N, the optical MUX 1040can multiplex the N outbound optical signals into a multiplexed transmitoptical signal that can be transmitted over a single physical link. Theoptical DEMUX 1050 performs the inverse of the MUX 1040, receiving amultiplexed receive optical signal that can be demultiplexed into Nreceive optical signals. The N receive optical signals can be convertedto N electrical signals by the ROSAs 1030A through 1030N and processedfurther by electrical components on the PCB 1010.

Each of the ITMs 1020A through 1020N can require less space thanrequired for a conventional TOSA and corresponding CDR, driver, and/ormicrocontroller, and/or linear amplifier. Accordingly, the size of amulti-channel optoelectronic device 1000 having a plurality of ITMs andan optical MUX 1040 and/or DEMUX 1050 can be smaller than a conventionalmulti-channel optoelectronic device having a plurality of TOSAs andcorresponding CDRs, drivers, and/or microcontrollers, and/or linearamplifiers, and an optical MUX and/or DEMUX. This can enable arelatively smaller form factor, resulting in greater port density, foroptoelectronic devices 1000 as compared to their conventionalcounterparts.

In FIG. 11, some or all of the extra real estate made available on a PCB1110 by removing electronic components from the PCB 1110 to an ITM 1120can be eliminated to make room for a polarization controller 1140, whichmay be operably connected to the optical output of the ITM 1120.Generally speaking, a polarization controller controls the polarizationof optical signals emitted by the ITM 1120. For instance, thepolarization controller 1140 can be used for polarization modedispersion (“PMD”) compensation. PMD is a form of modal dispersion wheretwo orthogonally polarized parts or polarization modes of an opticalsignal travel through an optical fiber at different speeds, leading to atemporal broadening of the signal. PMD results from random imperfectionsin the radial symmetry of the optical fiber, which may arise during theproduction process and/or due to environmental factors such astransverse stress, bending, twisting, aging, etc.

PMD compensation can be performed by splitting the optical output of theITM 1120 into two principal polarizations using the polarizationcontroller 1140 and applying a differential delay to bring them backinto synch. Due to the fact that PMD effects are random andtime-dependent, the polarization controller 1140 can be implemented asan active device that responds to feedback over time. In this case, afeedback loop can be provided for the polarization controller 1140.While the device 1100 has been discussed in the context of PMDcompensation, the polarization controller 1140 can alternately oradditionally be used for polarization scrambling, polarizationmultiplexing, as a polarization generator, and the like or anycombination thereof.

In FIG. 12, some or all of the extra real estate made available on a PCB1210 by removing electronic components from the PCB 1210 to an ITM 1220can be eliminated to make room for an optical power monitoring device1240, which can be operably connected to the optical output of the ITM1220. Many systems in which optoelectronic devices are implemented canrequire accurate measurement of the optical power emitted by an opticaltransmitter to optimize system performance. For instance, optical powermonitoring can be used to ensure a constant output from an opticaltransmitter whose output may vary with temperature and/or age. While thedevice 1200 discloses an optical power monitoring device 1240 externalto the ITM 1220, the optical power monitoring device 1240 can also beplaced inside the ITM 1220 with a corresponding increase in size of theITM 1220.

According to embodiments of the invention, the optical power monitoringdevice 1240 may include a photodetector. Where the optical transmitterused inside the ITM 1220 is an edge emitter, the transmission signal isemitted from the front of the emitter towards an optical fiber andanother signal can be emitted from the back of the emitter. The opticalpower of the light signal emitted from the rear of the emitter isproportional to the optical power of the transmission signal emittedfrom the front of the emitter. Consequently, the optical powermonitoring device 1240 can be placed inside the ITM 1220 to the rear ofthe emitter to monitor optical power without interfering with thetransmission signal. Numerous other optical power monitoring device 1240configurations can be implemented in embodiments of the invention andthe invention should not be limited to the specific configurationdescribed herein.

One skilled in the art will appreciate, with the benefit of the presentdisclosure, that the example embodiments disclosed in FIGS. 2-12 are notmutually exclusive and can be combined in a variety of ways. Further,the disclosed embodiments are provided by way of example only, and notby way of limiting the scope of the claimed invention.

In any event, due to the space and power budget savings obtained byusing an ITM, rather than a TOSA and corresponding electronic componentson a PCB, in an optoelectronic device, one or more of theabove-described electronic and optical components can be included in anoptoelectronic device that conforms to, e.g., the XFP form factor MSA,the 300-pin MSA, and the like. To better understand how the space andpower budget savings can be obtained, reference will now be made toFIGS. 14A-18, which describe intelligent transmitter modules andcomponents thereof according to embodiments of the invention.

III. Intelligent Transmitter Module

FIGS. 14A and 14B depict two embodiments of an intelligent transmittermodule in simplified block form that may be implemented in embodimentsof the invention. In FIG. 14A, ITM 1400 includes a first substrate 1414and a second substrate 1416. Various electronic components typicallybonded to or manufactured on the PCB of a conventional optoelectronicdevice are bonded to or manufactured on the first substrate 1414,including a CDR and driver IC 1402, a thermal chirp compensation (“TCC”)circuit 1404, and a linear amplifier 1406. The second substrate 1416includes a laser with managed chirp 1408, which is one type of opticaltransmitter that can be implemented in embodiments of the invention.Embodiments of a laser with managed chirp are marketed by the FinisarCorporation as Chirp Managed Laser CML™ transmitters.

In FIG. 14B, ITM 1450 also includes a first substrate 1460 and a secondsubstrate 1470. The first substrate 1460 includes various electroniccomponents, including a CDR and driver IC 1462 and a microcontroller1464. The second substrate 1470 includes an optical transmitter 1472. Itis appreciated that the embodiments of FIGS. 14A and 14B areillustrative only and that different and/or additional electronic and/oroptical components (other than those illustrated) can be included in anITM. For instance, the ITM 1400 of FIG. 14A may have an opticaltransmitter other than a laser with managed chirp 1408, can additionallyinclude a microcontroller bonded to the first substrate 1414, and/or canadditionally include other components such as an optical powermonitoring device, an SOA, and the like. Alternately or additionally,the ITM 1450 of FIG. 14B may include a linear amplifier, TCC circuit,optical power monitoring device, SOA, and the like, and/or thetransmitter 1472 may comprise a laser with managed chirp.

In operation, the ITM 1400 of FIG. 14A receives a differentialelectrical signal 1418 for transmission as a data-carrying opticalsignal. At the CDR and driver IC 1402, the electrical signal isequalized and retimed by a CDR stage. Alternately or additionally, theCDR stage can recover a clock from the electrical signal for use in atransponder, for instance. The CDR stage can equalize and retime thesignal 1418 using a clock signal from a host, using the data signalitself, or any combination thereof. Alternately or additionally, the CDRstage can be bypassed.

The output of the CDR stage is provided within the CDR and driver 1402to a driver stage configured to generate a modulation signal. In oneembodiment, the driver stage includes a VCSEL driver capable of driving50 ohm impedance loads. The driver stage of the CDR and driver 1402 maybe further configured to perform wave-form shaping of the retimedelectrical data signal, including pre-emphasis, de-emphasis, jitterpre-compensation, asymmetric rise fall time, asymmetric boost,cross-point adjust, modulation amplitude adjust, polarity control, laserDC bias control, and the like or any combination thereof.

For long-wave applications and in other embodiments of the invention,the modulation signal can be amplified by linear amplifier 1406 prior tobeing provided to the laser 1408, which emits an optical signalrepresentative of the electrical signal 1418. As will be discussed ingreater detail below, the operation of the laser 1408 depends onmanaging the chirp of a distributed feedback (“DFB”) or other laser. Forthis reason, the TCC circuit 1404 can be included in the ITM 1400 forproviding thermal chirp compensation. As shown, the ITM 1400 mayinteract with an external microcontroller configured to perform digitaldiagnostic functions and/or to optimize performance of the ITM 1400.

The operation of the ITM 1450 of FIG. 14B is similar to that of ITM1400. The ITM 1450, however, may be configured for short-waveapplications (e.g., 850 nm) as shown and can include a vertical cavitysurface emitting laser (VCSEL) or other short-wave transmitter 1472. Inthis case, the output of the CDR and driver IC 1462 can be used todirectly drive transmitter 1472 to emit an optical signal representativeof the electrical signal 1468. Additionally, the ITM 1450 can include aninternal microcontroller IC 1464 configured to perform digitaldiagnostic functions and/or to optimize the performance of the ITM 1450.For instance, the microcontroller may monitor transmitter temperature,transmitter optical output power, and the like or any combinationthereof. Further, the microcontroller 1464 may adjust settings on theCDR and driver IC 1462 and/or transmitter 1472. In some embodiments ofthe invention, the microcontroller 1464 (or an externally providedmicrocontroller in the embodiment of FIG. 14A) may facilitate wavelengthlocking, filter tuning, electrical cross point adjust, thermal chirpmanagement control, and the like or any combination thereof.

While the embodiments of FIGS. 14A and 14B have been described asimplementing a laser with managed chirp or a short-wave VCSEL, othertransmitters having any suitable configuration can alternately beimplemented. For instance, the transmitter used in the embodiments ofFIG. 14A or 14B may alternately or additionally comprise a laserintegrated modulator (“LIM”), a DFB laser, a cooled or uncooledexternally modulated laser (“EML”), an EML with a wavelocker, a cooledor uncooled directly modulated laser (“DML”), a DML with a wavelocker,and the like or any combination thereof. Further, the transmitters 1408,1472 can be configured to operate at data rates of 10 gigabits persecond and more.

According to embodiments of the invention, the ITMs 1400, 1450 can beconfigured to support multiple communication protocols, including two ormore of SONET, SDH, Ethernet, Fiber Channel, and others. In order tosupport multiple protocols, the ITMs 1400, 1450 can include the CDRstage of the IC 1402, 1462 for equalization and retiming of theelectrical data signal 1418, 1468 and/or clock recovery. As alreadymentioned, the CDR stage can be bypassed where clock recovery and/orequalization and retiming of the electrical data signal is not required.For instance, a host can communicate with a microcontroller external orinternal to the ITMs 1400, 1450 over a suitable interface (e.g., SPI,MDI, I²C, etc.) to identify whether equalization and retiming isnecessary. Accordingly, the microcontroller can then control the CDRstage of the CDR and driver IC 1402, 1452 to equalize and retime theelectrical data signal 1418, 1468 or not.

In some embodiments of the invention, electronic components (e.g.,linear amplifier IC, CDR and driver IC, and the like) within the ITM1400 (and/or 1450) can be flip chip bonded to the first substrate 1414.Flip chip bonding can reduce the length of the interconnects between theICs 1402, 1406 and the substrate 1414 to which the ICs are attached,thereby reducing signal degradation due to cross talk and parasiticcapacitance and reducing EMI, etc. Notwithstanding the advantages offlip chip bonding, other bonding techniques may alternately oradditionally be used to operably connect the ICs 1402, 1406 to thesubstrate 1414, including wire bonding, through-hole construction, andsurface mount technology.

The substrate 1414 may comprise, for instance, multilayer high frequencylaminate or silicon wafer, and the like or any combination thereof.Alternately or additionally, the substrate 1414 may comprise hybridceramic or thin film. In embodiments in which a laminate is implemented,the substrate can include a first layer for a transmission line, asecond layer for ground, a third layer for a power plane, and the likeor any combination thereof. The substrate 1414 may include blind and/orburied vias for electrically connecting components (e.g., ICs 1402 and1406, passive elements such as filters, and the like) to the substrate1414.

In embodiments of the invention, the ITM 1400 (and/or 1450) can behermetically sealed within a faraday cage to reduce the effects of EMIon the ITM and/or from the ITM. In this case, the number of high speedfeedthroughs may be limited to as few as three: e.g., two for anincoming differential signal and one for ground. Various low speed DCfeedthroughs, which may be easier and less expensive to make than highspeed feedthroughs, can be provided as well, e.g., I_(Bias), TEC1⁺,TEC1⁻, TEC2⁺, TEC2⁻, Vcc1 (for the CDR and driver), Vcc2 (for the linearamplifier), ground, various control lines to interface with an externalmicrocontroller, and the like or any combination thereof.

According to embodiments of the invention, an ITM 1400 or 1450 can beoperated within a transceiver, transponder, or other module. In thiscase, the ITM 1400 or 1450 can be operably connected to a PCB or othercircuitry within the module using a flex circuit to preserve signalintegrity from the PCB to the ITM. Note, however, that since the ITMincludes a CDR, leads can also be used between the PCB and ITM andlosses in signal integrity due to the use of leads can be recovered bythe CDR.

A. Integrated CDR and Driver IC

One example of an integrated CDR and driver that can be implementedwithin an ITM 1400, 1450 and/or in other environments is depicted inFIG. 15A. The integrated CDR and driver 1500 includes an input stage1502, a CDR or equalization and retiming stage 1504, and a driver stage1510 that can include waveform shaping 1512 and an output stage 1514. Anincoming electrical data signal, which may comprise a differentialsignal pair, can be received at the input stage 1502 and provided to theCDR stage 1504 for equalization and retiming and/or clock and datarecovery. The CDR stage 1504 can include a phase-locked loop (“PLL”)1506 and frequency-locked loop (“FLL”) 1508.

Once the electrical signal has been equalized and retimed, it can beprovided to the driver stage 1510 where it can be shaped and optimizedfor transmission as an optical signal. The driver stage 1510 cancomprise a high current switching driver, such as a VCSEL modulatorcapable of driving 50 ohm impedance loads, although this is not requiredin all embodiments. Further, the driver stage 1510 may include waveformshaping features. For instance, the driver stage 1510 can be configuredto perform one or more of: pre-emphasis, de-emphasis, jitterpre-compensation, asymmetric rise/fall time, asymmetric boost, and thelike or any combination thereof. Finally, the equalized, retimed, andreshaped electrical data signal is provided to the output stage 1514 foroutput.

Details regarding an example of the CDR stage 1504 are illustrated inFIG. 15B, which illustrates CDR 1504 with PLL 1506 and FLL 1508. The FLL1508 can include a phase frequency detector (“PFD”) 1510, a PFD chargepump 1512, a loop filter 1514, a voltage-controlled oscillator (“VCO”)1516, capacitor select logic 1518, a bit-error detector 1521, and BERcounter 1522. The FLL 1508 may have a broader acquisition range than thePLL 1506 and can be used to lock the VCO frequency onto the frequency ofa reference signal, which in some embodiments may include the incomingelectrical data signal 1520. The PFD 1510 can monitor the referencesignal frequency and the VCO frequency, generating a signal indicating afrequency-locked condition when the two frequencies are equal (or withina certain margin).

The PLL 1506 can include a voltage-controlled phase shifter 1524, aphase detector (“PD”) 1526, a PLL charge pump 1528, and the VCO 1516.Once the frequency has been locked, the PLL 1506 can drive any remainingfrequency error to zero and align the clock to the phase of theelectrical data signal for the retiming function.

Frequency equalization can help reduce jitter generation underband-limited input signal conditions and the use of a separate PLL andFLL can reduce the likelihood of false locking. Additionally, the PLL1506 can be a dual-loop PLL which can provide for low jitter generationand high tolerance. Further, the FLL 1508 can include BER detector 1520and PFD 1510 with LOL detect and switch-able capacitors, the combinationof which can provide for a wide pull-in range over process corner andbit rates. One skilled in the art will additionally appreciate, with thebenefit of the present disclosure, that the capacitor select logic 1518and switch-able capacitors may enable dynamic trimming of the VCO 1516at insertion of the electrical signal, thereby eliminating the need totest and trim in the factory.

Returning to FIG. 15A, it will be appreciated by those skilled in theart that the integration of the CDR 1504 and driver stage 1510 on asingle IC is not a trivial matter; various obstacles must be overcome toensure proper functioning of the integrated component. For example,operation of a CDR is optimized in a low-noise environment. However, adriver is an inherently high-noise circuit. Consequently, a conventionalCDR fabricated on the same die as a conventional driver will notfunction properly since the noise from the driver can be picked up bythe VCO of the CDR, thereby preventing phase detection and/or frequencyacquisition.

Accordingly, in some embodiments of the invention the CDR and driver canbe separately grounded. Furthermore, capacitive couplings can be used toisolate the CDR from the driver.

While FIG. 15A illustrates the CDR 1504 and driver 1510 as beingintegrated in a single IC, in other embodiments the CDR and driver canbe implemented in separate ICs. Whether implemented with or without adriver, the CDR 1504 can help preserve key microwave and/or SONETtransmission performance parameters. Thus, data retiming andregeneration (provided by the CDR 1504) can be implemented to processSONET signals which typically include phase delay, rise-fall timedegradation, BW degradation, and so on.

B. Linear Amplifier

Turning now to FIG. 16, one embodiment of a linear amplifier 1600 isdepicted that may be implemented in embodiments of the invention. Thelinear amplifier 1600 may correspond to the linear amplifier 1406 ofFIG. 14A and can be operated to drive the transmitter 1408 where themodulation signal provided by the integrated CDR and driver 1402 isinsufficient to properly drive the transmitter and/or in othercircumstances.

The linear amplifier 1600 can be configured to be operably coupledbetween a driver output (not shown) and an optical transmitter 1660,each of which may correspond to, respectively, the driver output of IC1402 and optical transmitter 1408 of FIG. 14A. As shown, the linearamplifier circuit can include two input nodes 1602A and 1602B forreceiving a differential signal from the driver, a buffer stage 1610, anamplifier stage 1620, a VCM 1630, a feedback loop or bias circuit 1640,and an optional thermal chirp compensation (“TCC”) circuit 1650.

The input nodes 1602A, 1602B may include AC-coupling capacitors,although this is not required in all embodiments. The buffer stage 1610can include one or more transistors 1611-1613 and one or more resistors1614-1618. The amplifier stage 1620 can include one or more transistors1621 and one or more resistors 1622. The bias circuit 1640 can includeone or more transistors 1641-1642, one or more capacitors 1643, one ormore resistors 1644-1646, and a current mirror 1647.

The transistors depicted in FIG. 16 may include bipolar transistors,although this is not required in all embodiments. For instance, thetransistors of FIG. 16 may alternately or additionally includefield-effect transistors without altering the theory, spirit andadvantages of embodiments of the invention.

Decoupling circuit 1604 can be provided between supply node 1670 andsignal ground 1680 such that signal ground 1680 does not need to be anRF ground. While illustrated as including a decoupling capacitor 1604A,one skilled in the art should appreciate that the decoupling circuit1604 can be more complicated in order to address different ranges offrequencies of interest. Thus, the decoupling circuit 1604 mayalternately or additionally include capacitors, resistors, inductors,and the like.

In operation, a differential signal can be received from the driveroutput stage (not shown) by the buffer stage 1610. The buffer stage 1610can convert the differential signal to a single-ended signal and provideit to the amplifier stage 1620, sending it from the emitter terminal ofbuffer stage transistor 1613 to the base terminal of amplifier stagetransistor 1621. The amplifier stage transistor 1621 can pull currentthrough the transmitter 1660, the magnitude of the current pulledthrough the transmitter being directly proportional to the currentreceived from the buffer stage transistor 1613. Accordingly, thesingle-ended signal received from the buffer stage transistor 1613 canbe amplified by the amplifier stage transistor 1621 and the transmitter1660 can then emit an optical signal representative of the amplifiedsignal. The electrical signals can then be returned to signal ground1680, the signal ground 1680 being separate from a header or chassisground.

Although not required in all embodiments, the circuit 1600 can include aTCC circuit 1650, as disclosed in FIG. 16. The TCC circuit 1650 can beadapted for operation with a laser with managed chirp, embodiments ofwhich are described herein. As shown, the TCC circuit 1650 can include acurrent summing circuit 1651, a gain stage 1652, and a filter 1653, andcan be configured to adjust the bias current bias supplied to theoptical transmitter 1660 up or down to compensate for thermal chirp andmaintain operation of the transmitter 1660 at a fixed wavelength.

Briefly, chirp is the frequency modulation of an emitted optical signalresulting when a transmitter, such as a DFB laser, is directlymodulated. A directly modulated DFB laser exhibits three types of chirp:(1) transient chirp, (2) adiabatic chirp, and (3) thermal chirp.Transient chirp has a short-term damped oscillatory behavior and occursat 1-to-0 and 0-to-1 bit transitions. Transient chirp is usuallyundesirable, but can be controlled to manageable levels through properbiasing of the transmitter. Adiabatic chirp is proportional to opticalintensity, causing 1 bits to be blue-shifted relative to 0 bits. Whileundesirable in many instances, adiabatic chirp can be managed, and infact can be central to using a laser with managed chirp, as discussedbelow. Thermal chirp has the opposite sign of adiabatic chirp and has adelayed response to an applied current, the response increasingexponentially in time. Thermal chirp is generally undesirable.

Thermal chirp is affected by the mark density (e.g., the ratio of 1 bitsto total bits) of a bit sequence. While the mark density for a randombit sequence averages to ½, local segments of the sequence may have ahigher or lower mark density. For a directly modulated DFB laser, a highdensity of 1's will tend to heat the laser since the average injectioncurrent is increased, while a high density of 0's will tend to cool thelaser. The change in temperature of the laser can change the refractiveindex of the laser, resulting in a change in laser frequency. Hence, thetemperature of the laser and its optical frequency tend to wander overtime in response to short term changes in the mark density of the bitsequence.

When the DFB laser is used in a laser with managed chirp, an opticalspectrum reshaper (“OSR”) converts the frequency wander to amplitudewander, causing the amplitude of the 1 and 0 bits to change slowly atthe output of the laser with managed chirp depending on the mark densityof the applied system. Additionally, frequency wander caused by thermalchirp can cause variations in the arrival time of the bits at a receiverwhen the emitted signal is transmitted over a dispersive fiber. Both ofthese consequences are generally undesirable.

However, to compensate for thermal chirp and eliminate or reduce thesedeleterious consequences, the TCC circuit 1650 can identify long stringsof 1s or 0s and cause the bias circuit 1640 to adjust the transmit powerof the transmitter 1660 up or down as needed to maintain the desiredchirp.

C. Laser with Managed Chirp

Turning now to FIG. 17, one embodiment of a laser with managed chirp1700 is illustrated that can be implemented in embodiments of theinvention. The laser with managed chirp 1700 may correspond to thetransmitter 1408 of FIG. 14A or the transmitter 1472 of FIG. 14B. Theprimary components of the module 1700 are an optical signal source 1702such as a DFB laser and an optical spectrum reshaper (“OSR”) 1710 ormulti-cavity etalon filter. Basically, the OSR 1710 converts a frequencymodulated signal of the optical signal source 1702 to an amplitudemodulated signal and additionally introduces phase correlation betweenthe bits of the signal.

The laser with managed chirp 1700 can additionally include supportingoptics and various electronic components. The support optics can includea beam splitter 1704 and power and wavelength detecting photodiodes 1706and 1706. The electronic components can include a first thermistor 1712for monitoring the temperature of the laser 1702, a second thermistor1714 for monitoring the temperature of the OSR 1710, a firstthermoelectric cooler (“TEC”) 1716 for regulating the temperature of thelaser 1702, and a second TEC 1718 for regulating the temperature of theOSR 1710.

The laser 1702 can be a directly modulated DFB laser in the exampleshown in FIG. 17, or other suitable optical signal source. For instance,the laser 1702 can alternately be an externally modulated DFB laser, ora LIM, in which case the TEC 1718, OSR 1710, and thermistor 1714 couldbe omitted. Alternately, the laser 1702 may include a VCSEL with a 30 mAmaximum bias current, in which case the TEC 1716 and thermistor 1712could be omitted, and a CDR and driver IC could drive the laser 1702without a linear amplifier, as illustrated in FIG. 14B.

A module 500 manages the chirp of a transmitter 1702 to optimize asignal produced by the transmitter. As mentioned above, when asemiconductor transmitter such as a DFB is directly modulated, threetypes of chirp are exhibited: transient chirp, which occurs at bittransitions and hastens pulse spreading in fibers with positivedispersion; adiabatic chirp, which makes 1 bits blue-shifted relative to0 bits; and thermal chirp, which as the opposite sign of adiabatic chirpand increases exponentially in time. Conventional DML transmitters arebiased near threshold, in which case transient chirp dominates andprevents the use of the DML in long-haul applications due to pulsespreading, which results in rapid distortion in the eye afterpropagation.

However, the laser 1702 can be biased high above threshold to reducetransient chirp, which can also lead to a low extinction ratio at thelaser output. While transient chirp is reduced, the low extinction ratioat the laser output can be problematic for signal propagation. However,the extinction ratio can be increased using the OSR 1710. The OSR 1710can include a filter with a transmission window configured todiscriminate between blue-shifted 1 bits and red-shifted 0 bits.Consequently, the OSR 1710 can transmit 1 bits with little or no losswhile attenuating 0 bits to increase the extinction ratio of the signal.In addition, the OSR 1710 can form a wavelength locker together with thetwo photodiodes 1706, 1708 and the beam splitter 1704. Thermal chirp canbe managed as described above using a TCC circuit.

Adiabatic chirp, together with the OSR 1710, can introduce phasecorrelation between the bits, which can increase dispersion toleranceand reduce the information bandwidth by a factor of two. Consider a “1 01” bit sequence at 10 G where 1 bits have 5 GHz higher frequency than 0bits. The phase of the carrier slips by 2π×5 GHz×100 ps=π during the 0bit, making the second 1 bit π out of phase with the first. Normallydispersion closes the eye by spreading the energy of the 1 bits intoadjacent 0 bits. Here, the 1 bits interfere destructively in the middle0 bit because of the π phase shift, keeping the eye open after fiberpropagation.

The wavelength locker can be operated by detecting a photocurrent fromeach of the photodiodes 1706 and 1708. The photocurrents can be providedto a microcontroller which can use a lookup table or other means todetermine the wavelength of the emitted signal based on thephotocurrents. A temperature measurement from the thermistor 1714 can beused by the microcontroller to determine the transmission window of theOSR 1710. The transmission window can be changed and the wavelength ofthe signal locked onto by changing the temperature of the OSR 1710 usingthe TEC 1718. Alternately or additionally, the wavelength of the emittedsignal can be changed by increasing or decreasing the temperature of thetransmitter 1702 using the TEC 1716.

More details regarding lasers with managed chirp are provided in U.S.patent application Ser. No. 10/289,944, filed Nov. 6, 2002, which isincorporated herein by reference in its entirety.

D. Microcontroller

With reference now to FIG. 18, one embodiment 1800 of a microcontrolleris illustrated that can be integrated within an intelligent transmittermodule or implemented in conjunction therewith. In the embodimentillustrated in FIG. 18, the microcontroller 1800 can include both ananalog portion 1802 and a digital portion 1804 that together allow themicrocontroller to implement logic digitally, while still largelyinterfacing with other components (e.g., a transmitter, etc.) usinganalog signals.

The analog portion 1802 may contain digital to analog converters(“DACs”) 1806, analog to digital converters (“A2Ds”) 1808, high speedcomparators (e.g., for event detection), voltage based reset generators,voltage regulators, voltage references, a clock generator, and otheranalog components. The analog portion 1802 may also include sensor 1814Aamongst potentially others as represented by the horizontal ellipses1814B. Each of these sensors may be responsible for measuringoperational parameters such as, for example supply voltage andtransceiver temperature. The microcontroller 1800 may also receiveexternal analog signals from a laser with managed chirp or othercomponent in order to monitor the laser with managed chirp. Fourexternal lines 1816A, 1816B, 1816C and 1816D are illustrated forreceiving such external analog signals, although there may be many ofsuch lines. According to one embodiment of the invention, each of theexternal lines receives one of the photocurrents from the photodiodes1706, 1708 or one of the temperatures from the thermistors 1712, 1714 ofFIG. 17.

The internal sensors 1814A through 1814B may generate analog signalsthat represent the measured values. In addition, the externally providedsignals 1816A through 1816D may also be analog signals. In this case,the analog signals are converted to digital signals so as to beavailable to the digital portion 1804 of the controller 1800 for furtherprocessing. Of course, each analog parameter value may have its own A2D.However, to preserve chip space, each signal may be periodically sampledin a round robin fashion using a single A2D such as the illustrated A2D1808. In this case, each analog value may be provided to a multiplexer1818, which selects in a round robin fashion, one of the analog signalsat a time for sampling by the A2D 1808. Alternatively, multiplexer 1818may be programmed to allow for any order of analog signals to be sampledby the A2D 1808.

The digital portion 1804 of the control module 1800 may include a timermodule 1820 that provides various timing signals used by the digitalportion 1804. Such timing signals may include, for example, programmableprocessor times. The timer module 1820 may also act as a watchdog timeror countdown timer.

Two general purpose processors 1822 and 1824 are also included. Theprocessors recognize instructions that follow a particular instructionset, and may perform normal general-purpose operations such as shifting,branching, adding, subtracting, multiplying, dividing, Booleanoperations, comparison operations, and the like. In one embodiment, thegeneral-purpose processors 1822 and 1824 are each a 16-bit processor andmay be identically structured. The precise structure of the instructionset is not important to the principles of the present invention as theinstruction set may be optimized around a particular hardwareenvironment, and as the precise hardware environment is not important tothe principles of the present invention.

A host communication interface 1826 can optionally be implemented tocommunicate with a host using, for example, serial data (SDA) and serialclock (SCL) lines of an I²C interface, although other interfaces,including SPI, MDIO, 1-wire, and the like may also be used. An externaldevice interface 1828 can be implemented to communicate with othermodules within an intelligent transmitter module such as the integratedCDR and VCSEL driver and/or linear amplifier as well as to communicatewith other modules within an optical transceiver or transponder, such asa post-amplifier, and the like.

The internal controller system memory 1830 may be random access memory(RAM) or nonvolatile memory. While system memory 1830 may be RAM, it mayalso be a processor, register, flip-flop or other memory device. Thememory controller 1832 shares access to the controller system memory1830 amongst each of the processors 1822, 1824, the host communicationinterface 1826 and the external device interface 1828. According to oneembodiment of the invention, information can be logged within the systemmemory 1830 and later retrieved for diagnosing an intelligenttransmitter module or other device within which the microcontroller 1800is implemented.

An input/output multiplexer 1834 multiplexes the various input/outputpins of the microcontroller 1800 to the various components within themicrocontroller 1800. This enables different components to dynamicallyassign pins in accordance with the then-existing operationalcircumstances of the microcontroller 1800. Accordingly, there may bemore input/output nodes within the microcontroller 1800 than there arepins available on the microcontroller 1800, thereby reducing thefootprint of the microcontroller 1800.

As previously mentioned, the microcontroller 1800 can be implemented onits own IC within an optoelectronic device or can be integrated on thesame IC as an integrated CDR and driver and/or linear amplifier.Integrating the microcontroller into an IC with these other componentsis not simply a matter of fabricating a conventional microcontroller onthe same die as a conventional CDR, driver, and/or linear amplifier. Forinstance, high speed signals within the digital core 1804 can interferewith functions performed by the aforementioned components. Additionally,noise from the driver can interfere with the analog portion 1802. Forthis reason, the analog and or digital portions of the microcontroller1800 may be capacitively coupled and/or ground separation can beprovided.

Additionally, when implemented in conjunction with a laser with managedchirp or other transmitters for high speed (e.g., 10 G and higher) andlong haul optical communication, functionality and capabilities beyondthose currently offered by conventional microcontrollers can be includedin the microcontroller. For instance, proper operation of a laser withmanaged chirp at high speeds can involve rapid and repetitious readingof the temperatures of one or more TECs, reading the photocurrent fromtwo or more photodiodes, updating the driver to maintain a particularextinction ratio, communicating with the CDR to ensure data flow,communicating with a TCC circuit to adjust gain, and the like.Accordingly, the microcontroller can include two processors 1824, 1822that enable proper processing of incoming and outgoing control data. Forexample, in some embodiments, one of the processors can handles all highspeed processes while the other processor handles all low speedprocesses in the background.

In some instances, proper operation of the laser with managed chirp mayinclude measuring the temperature of the TECs to an accuracy of ±0.01degrees Celsius. However, conventional microcontrollers are only able tomeasure temperature to an accuracy of approximately ±3 degrees Celsiusbecause the A2Ds used only have 10-bit resolution. Accordingly,embodiments of the invention can implement a 14-bit or higher A2D,although not required in all embodiments. Alternately or additionally,relative to a general purpose microcontroller, the microcontroller 1800can be simplified in some respects to optimize its functionality withinan intelligent transmitter module.

The integration of one or more electronic components (including the CDR,driver, linear amplifier, and microcontroller) within an intelligenttransmitter module can result in the removal of these components fromtheir conventional location on a PCB, thereby freeing up real estate onthe PCB. As described in greater detail above, various other componentscan be implemented in a transceiver, transponder, or othercommunications module using the additional real estate made available byusing an ITM. These other components may include one or more of an FPGA,a digital signal processor, a memory chip, a digital diagnostic IC, awireless and/or RF interface for interoperability communications (e.g.,RF on fiber), video electronic circuitry, a VOA, an SOA, an optical MUXand/or DEMUX, and optical monitoring device, a polarization controller,and the like or any combination thereof.

The embodiments described herein may include the use of a specialpurpose or general-purpose computer including various computer hardwareor software modules, as discussed in greater detail below.

Embodiments within the scope of the present invention also includecomputer-readable media for carrying or having computer-executableinstructions or data structures stored thereon. Such computer-readablemedia can be any available media that can be accessed by a generalpurpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium which can be used to carryor store desired program code means in the form of computer-executableinstructions or data structures and which can be accessed by a generalpurpose or special purpose computer. When information is transferred orprovided over a network or another communications connection (eitherhardwired, wireless, or a combination of hardwired or wireless) to acomputer, the computer properly views the connection as acomputer-readable medium. Thus, any such connection is properly termed acomputer-readable medium. Combinations of the above should also beincluded within the scope of computer-readable media.

Computer-executable instructions comprise, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions. Although the subject matter has been described inlanguage specific to structural features and/or methodological acts, itis to be understood that the subject matter defined in the appendedclaims is not necessarily limited to the specific features or actsdescribed above. Rather, the specific features and acts described aboveare disclosed as example forms of implementing the claims.

As used herein, the term “module” or “component” can refer to softwareobjects or routines that execute on the computing system. The differentcomponents, modules, engines, and services described herein may beimplemented as objects or processes that execute on the computing system(e.g., as separate threads). While the system and methods describedherein are preferably implemented in software, implementations inhardware or a combination of software and hardware are also possible andcontemplated. In this description, a “computing entity” may be anycomputing system as previously defined herein, or any module orcombination of modulates running on a computing system.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. An optoelectronic device for transmitting optical signals, the devicecomprising: an intelligent transmitter module, including: a clock anddata recovery circuit for receiving an electrical data signal; a driveroperably connected to the clock and data recovery circuit and configuredto generate a modulation signal from the electrical data signal; alinear amplifier operably connected to the driver and configured toreceive and amplify the modulation signal; and an optical transmitteroperably connected to the linear amplifier, the optical transmitterconfigured to receive the amplified modulation signal and emit anoptical data signal representative of the electrical data signal; and aprinted circuit board configured to carry the electrical data signal tothe intelligent transmitter module, the printed circuit board beingoperably connected to the intelligent transmitter module.
 2. Theoptoelectronic device of claim 1, further comprising a fieldprogrammable gate array coupled to the printed circuit board.
 3. Theoptoelectronic device of claim 2, wherein the field programmable gatearray is programmed to implement one or more digital signal processingalgorithms on the electrical data signal prior to the electrical datasignal.
 4. The optoelectronic device of claim 1, further comprising amemory chip coupled to the printed circuit board.
 5. The optoelectronicdevice of claim 1, further comprising a digital diagnostic integratedcircuit coupled to the printed circuit board and configured to generatemonitoring and operating data for the optoelectronic device.
 6. Theoptoelectronic device of claim 1, further comprising a video integratedcircuit coupled to the printed circuit board and configured to enablethe optoelectronic device to optically transmit video signals.
 7. Theoptoelectronic device of claim 1, further comprising one or both of: awireless interface coupled to the printed circuit board and configuredto receive a wireless data signal and generate the electrical datasignal, the electrical data signal being representative of the wirelessdata signal; or a radio frequency interface coupled to the printedcircuit board and configured to receive a radio frequency data signaland generate the electrical data signal, the electrical data signalbeing representative of the radio frequency data signal.
 8. Theoptoelectronic device of claim 1, further comprising one or both of: avariable optical attenuator operably connected to the intelligenttransmitter module and configured to adjustably reduce the power levelof the emitted optical data signal; or a semiconductor optical amplifieroperably connected to the intelligent transmitter module and configuredto increase the power of the emitted optical data signal.
 9. Theoptoelectronic device of claim 1, further comprising: a plurality ofintelligent transmitter modules, and an optical multiplexer operablyconnected to the optical output of the plurality of intelligenttransmitter modules and configured to multiplex a plurality of opticaldata signals received from the plurality of intelligent transmittermodules into a multiplexed optical data signal.
 10. The optoelectronicdevice of claim 1, further comprising a polarization controller operablyconnected to the intelligent transmitter module and configured tocontrol the polarization of the emitted optical data signal.
 11. Theoptoelectronic device of claim 1, further comprising an optical powermonitoring device operably connected to the intelligent transmittermodule and configured to monitor the power of the emitted optical datasignal.
 12. An optoelectronic device having one or more opticalcomponents and one or more electrical components, the device comprising:an intelligent transmitter module, including: a clock and data recoverycircuit for receiving, equalizing, and retiming an electrical datasignal; a driver operably connected to the clock and data recoverycircuit and configured to generate a modulation signal from theelectrical data signal; a laser operably connected to the driver andconfigured to emit an optical data signal representative of theelectrical data signal; and one or both of: a linear amplifier operablyconnected between the driver and the laser, the linear amplifierconfigured to receive and amplify the modulation signal; and amicrocontroller configured to control operation of the intelligenttransmitter module; a printed circuit board operably connected to theintelligent transmitter module for carrying the electrical data signalto the intelligent transmitter module; and a device housing forprotecting the printed circuit board and intelligent transmitter module.13. The optoelectronic device of claim 12, further comprising one ormore of: a field programmable gate array for performing one or moreprogrammable functions in the optoelectronic device; a digital signalprocessor for processing the electrical data signal; a memory chip; avideo integrated circuit; a wireless interface for receiving a wirelessdata signal and generating the electrical data signal therefrom; a radiofrequency interface for receiving a radio frequency data signal andgenerating the electrical data signal therefrom; a variable opticalattenuator operably coupled to the optical output of the intelligenttransmitter module for reducing the power level of the emitted opticaldata signal; a semiconductor optical amplifier operably coupled to theoptical output of the intelligent transmitter module for increasing thepower of the emitted optical data signal; a polarization controllerconfigured to control the polarization of the emitted optical datasignal; and an optical power monitoring device configured to monitor thepower of the emitted optical data signal.
 14. An optoelectronic devicecomprising: an intelligent transmitter module for receiving a firstelectrical signal and emitting an optical signal representative of thefirst electrical signal, the intelligent transmitter module including: afirst substrate having bonded thereto a first integrated circuit and alinear amplifier integrated circuit, the first integrated circuitincluding an equalization and retiming stage and a driver stage; and asecond substrate having manufactured thereon an optical signal source,wherein the optical signal source is operably connected to the linearamplifier integrated circuit; a receiver optical subassembly forreceiving an optical signal and converting the optical signal to asecond electrical signal; and a printed circuit board operably connectedto the intelligent transmitter module and the receiver opticalsubassembly and configured to carry the first electrical signal from ahost to the intelligent transmitter module and the second electricalsignal from the host to the receiver optical subassembly, wherein theprinted circuit board includes thereon a post amplifier for amplifyingthe inbound electrical signal.
 15. The optoelectronic device of claim14, further comprising one or more of: a field programmable gate arraycoupled to the printed circuit board and configured to be programmed bya user or manufacturer of the optoelectronic device; a memory chipcoupled to the printed circuit board for storing one or more of:microcode, information identifying the optoelectronic device, andoperational settings of the optoelectronic device; a polarizationcontroller coupled to the optical output of the intelligent transmittermodule, the polarization controller configured for one or more of:polarization mode dispersion compensation, polarization scrambling,polarization multiplexing, and a polarization generator; a photodetectorfor monitoring the optical power output of the intelligent transmittermodule; and a variable optical attenuator coupled to the optical outputof the intelligent transmitter module for adjustably attenuating theemitted optical signal, wherein the variable optical attenuatorcomprises a mechanical variable optical attenuator or a non-mechanicalvariable optical attenuator.
 16. The optoelectronic device of claim 14,further comprising a digital diagnostic integrated circuit coupled tothe printed circuit board, wherein the digital diagnostic integratedcircuit facilitates one or more of the following functions for theoptoelectronic device: device setup, device identification, eye safetyand general fault detection, temperature compensation, monitoring ofparameters relating to the optoelectronic device operatingcharacteristics and environment, tracking the amount of time theoptoelectronic device is powered on, and margining.
 17. Theoptoelectronic device of claim 14, further comprising a video integratedcircuit coupled to the printed circuit board and configured to process avideo signal for transmission as an optical signal by the intelligenttransmitter module, or to process a video signal received as an opticalsignal by the receiver optical subassembly, or any combination thereof,wherein the video integrated circuit comprises one or more of: a videodecoder, a video encoder, a video noise-reduction FIFO, an LCD graphicdisplay controller, a video FIFO, a video amplifier, and a video filter.18. The optoelectronic device of claim 14, further comprising a wirelessinterface coupled to the printed circuit board for: receiving a firstwireless signal and generating the first electrical signal, wherein thefirst electrical signal is representative of the first wireless signal;and receiving the second electrical signal and emitting a secondwireless signal representative of the second electrical signal.
 19. Theoptoelectronic device of claim 14, further comprising a radio frequencyinterface for: receiving a first radio frequency signal and generatingthe first electrical signal, wherein the first electrical signal isrepresentative of the first radio frequency signal; and receiving thesecond electrical signal and generating second radio frequency signalrepresentative of the second electrical signal.
 20. The optoelectronicdevice of claim 14, further comprising: a first semiconductor opticalamplifier coupled to the intelligent transmitter module and configuredto boost the emitted optical signal; and a second semiconductor opticalamplifier coupled to the receiver optical subassembly and configured topre-amplify the received optical signal.